1. Field of the Invention
Aspects of the invention relate to a plasma display device and a driving method thereof.
2. Description of the Related Art
A plasma display device is a flat panel display using a plasma display panel (PDP) that displays characters or images using plasma generated by a gas discharge. The plasma display panel includes, depending on its size, tens to millions of pixels arranged in a matrix.
The plasma display device divides each of a plurality of frames of a video signal into a plurality of subfields each having a grayscale weight for driving the plasma display panel to display grayscales. The grayscale of a discharge cell is determined by the sum of the grayscale weights of the subfields in which the discharge cell is driven to emit light. Each subfield has a reset period, an address period, and a sustain period. The reset period is for initializing the state of each discharge cell to facilitate performing an addressing operation in the discharge cell. The address period is for applying an address voltage to cells that are to be turned on (addressed cells) to generate an address discharge and store wall charges to select cells that are turned on and cells that are not turned on in the panel. The sustain period is for applying sustain pulses to perform a sustain discharge to display an image with the addressed cells.
In general, sustain pulses are applied to the scan electrode and the sustain electrode in the sustain period of each subfield, and a sustain discharge is accordingly generated in the discharge cells that were selected to be cells to be turned on in the address period. That is, sustain pulses alternately having a high level voltage (in general, a Vs voltage) and a low level voltage (in general, a 0V voltage) in opposite phases are applied to the scan electrode and the sustain electrode. A sustain discharge is then generated in discharge cells that have a voltage greater than a discharge firing voltage, i.e., that have a voltage that is the sum of the voltage due to the wall charges formed in the discharge cells that were selected to be cells to be turned on in the address period and the sustain pulse voltage difference. Respective grayscales can be expressed by a combination of grayscale weights of the subfields. Much power is consumed when there are many switching operations for applying a sustain pulse voltage to the scan electrode and the sustain electrode, that is, when many sustain pulses are applied to the scan electrode and the sustain electrode in a subfield.
Also, the plasma display panel (PDP) has a capacitance since the discharge space between the scan electrode and the sustain electrode of the plasma display panel functions as a capacitor. Therefore, reactive power must be supplied to charge the capacitance up to a predetermined voltage each time a sustain pulse is applied to the scan electrode and the sustain electrode, in addition to power that is consumed by the sustain discharge generated by the sustain pulses.
Furthermore, when one frame of the video expresses low grayscales over the entire display screen, or expresses a completely black image in which all of the discharge cells of the entire display screen express a 0 grayscale, undesired sustain pulses are applied in the sustain period of each subfield, further increasing power consumption.
The above information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention, and is not to be construed in any way as an admission that this information is prior art that was known by others in this country before the invention was made.